This invention relates to an atomic absorption spectrophotometer, and in particular to an atomic absorption spectrophotometer and an analyzing method therewith, which are suitable for quantitatively analyzing simultaneously a plurality of metallic elements of small quantity, which are resolved in an aqueous solution.
An atomic absorption spectrophotometer using a graphite furnace has different programs concerning the ashing temperature and the atomizing temperature for different elements, which are object to be measured, and effects quantitative analysis of the elements, which are objects to be measured, by transforming a sample to be measured into atomic vapor by heating the graphite furnace according to these temperature programs and by measuring the degree of light absorption while making light coming from a light source pass through this atomic vapor.
For an atomic absorption spectrophotometry using a graphite furnace an optimum temperature program is determined for every element, which is an object to be measured, taking the magnitude of the absorption sensitivity, the reliability, the life of the cuvette, etc. into account. The ashing temperature and the atomizing temperature according to this temperature program are determined, taking the following items into account.
i) Ashing temperature
The ashing temperature is a temperature set as high as possible as far as the aimed element is not atomized at this ashing step. When this temperature is too low, ashing is insufficient; components other than the aimed element remain; and background absorption at the atomizing step is increased, which reduces the reproducibility. On the other hand, when the ashing temperature is too high, the element to be measured is vaporized at the atomizing step. For this reason absorption peaks at the atomizing step become smaller, which reduces the sensitivity. As explained above, it is necessary to set the ashing temperature as high as possible as far as the aimed element is not vaporized at the ashing step.
ii) Atomizing temperature
The atomizing temperature is a temperature set sufficiently high for obtaining the greatest absorption of light having a specified wavelength due to the aimed element at the atomizing step. This is because the aimed element is not sufficiently atomized, which reduces the sensitivity, if the atomizing temperature is too low. For example for cadmium, which is a low melting point element, the ashing temperature is about 300.degree. C. and the atomizing temperature is about 1500.degree. C. On the other hand, for vanadium, which is a high melting point element measurements are effected with a temperature program, by which the ashing temperature is about 900.degree. C. and the atomizing temperature is about 3000.degree. C.
As described above, by the atomizing absorption spectrophotometry using a graphite furnace, since the optimum temperature program, i.e. ashing and atomizing temperatures, are determined for every element, heretofore measurement is effected for every single element.
As techniques relating to this invention, a method for obtaining the optimum ashing temperature and the optimum atomizing temperature is disclosed in JP-A-58-37540 (filed on Aug. 29, 1981 by Sumitomo Electric Industries, Ltd., Inventor: Masahiro Shibata). Further techniques for arranging a plurality of light sources at predetermined positions are disclosed in JP-A-63-292040.